Here, many of us use a deisel truck oil that is 15-40. Lovely stuff because it has the additives necessary for our motorcycle engines that have more stresses than car engines.Many also use motorcycle-specific 20-50.

I wouldn't worry about using a 10-40 until the temps stay on the 40's and lower. An even thinner grade would help start it perhaps, but I wouldn't think YOU could stand riding in zero degree weather.

Addendum; Just realized this is for a UCE (again). I would think a 10-40 would be fine until you get into the 90's or are stuck idling in heavy traffic a lot. The main thing is to use an oil made for motorcycles and change it fairly frequently.

Silkolene semi-synth 15-50 was in the bike (G5) when I got it, and what the dealer recommends, so I've stuck with it. Changed it twice since new - 2000 miles, and am about to again.Runs smooth with easy gear shifts.

Silkolene semi-synth 15-50 was in the bike (G5) when I got it, and what the dealer recommends, so I've stuck with it. Changed it twice since new - 2000 miles, and am about to again.Runs smooth with easy gear shifts.

There has been an issue of oil "coking" in the oil tube at the right side jug fins. This no doubt this could happen when residual oil sits in the tube and is cooked by the engine heat after shut down.Remedy.....well that's where the semi synthetic oil comes in.Its resist high heat "coking" problems.This is true in turbo charged cars as well. Oil "coking" up in the turbine oil drain or "scavenge" drain side was a problem due to the high heat in that area.

Armed with some oil knowledge , one can affordably put the right kind of oil to work , without losing sleep at night.

I currently use 15w -40 truck oil, but I know the conditions are fine for my climate and style of riding.

The book says 15W-50 - surely that's for Indian climate?Do I really need that multi-grade here in the UK? I would have thought a 10W-40 would be ideal for summer use and 5W-30 for Winter. I live in the North East - we get a lot of wind and rarely does it ever get above 30 degrees C even in high summer.

You do have an interesting point. I personally use 15W-50 in my G5 (Electra) in north east of US where the temperature is colder than in India. Only in the last few days the temperature has reached upto 30C. In my experience, this grade of oil works very well in warmer climate (above 20C) as we have right now. The gear changes and running, everything is smooth.

A few weeks back, when the weather was cooler and I rode it when the temperature was about 10C, the oil felt a bit too heavy. As Ernie has posted that 10W-40 may also be fine until you hit 32C or higher.

Addendum; Just realized this is for a UCE (again). I would think a 10-40 would be fine until you get into the 90's or are stuck idling in heavy traffic a lot. The main thing is to use an oil made for motorcycles and change it fairly frequently.

I change my motorcycle oil more frequently than recommended by Owners Manual. I like the engine, transmission and clutch plates run in clearner oil. It will pay off in the long run IMHO.